1. Technical Field
The present invention relates to a semiconductive belt, to a semiconductive roll, and to an image forming apparatus using these members.
2. Related Art
In an image forming apparatus utilizing an electrophotographic method, uniform electric charge is formed on a surface of a latent image carrier (photoreceptor (that is, the surface of the photoreceptor is uniformly electrically charged)). Then, an electrostatic latent image is formed by laser beams obtained by modulating image signals. Subsequently, a toner image is formed by developing an electrostatic latent image with charged toner. Then, the toner image is electrostatically transferred onto a recording medium through an intermediate transfer member or directly. Thus, a desired transfer image is obtained.
In recent years, such image forming apparatuses, for example, a printer and a copying machine have employed semiconductive members for various purposes. To aim for high picture quality, a long life, and environmental improvement, the semiconductive members have been achieving great progress. More specifically, examples of the uses of semiconductive members, such as a semiconductive rotating roll, are the overall basic processes of the electrophotographic method, for instance, electrification, exposure, development, transfer, cleaning, and neutralization processes.
For example, a transfer method using an intermediate transfer member employs a semiconductive endless belt (semiconductive belt). The semiconductive belt is generally made of an elastic material from the viewpoint of easiness of controlling thereof while driving. Generally, vulcanized rubber materials, for instance, ethylene-propylene-diene monomer (EPDM) rubber, urethane rubber, epichlorohydrin rubber, polychloroprene rubber, and blend rubber obtained by mixing these kinds of rubbers, are used as the elastic material.
A transfer/conveyance belt holds a method of holding a transferring material (recording medium) through an electrostatic adsorption force. Thus, to obtain favorable picture quality, uniformity of the in-plane resistance of the belt is necessary. This is because of the following facts. That is, in a case where the value of resistance is low at a part of the surface of the belt, an electric discharge occurs, so that the belt or the image carrier is damaged and that disturbance of an image transferred onto a surface of a transferring material occurs. Also, in a case where the volume resistivity value of the belt is high, an electric discharge phenomenon is caused by holding the transferring material at a high voltage. This results in a transfer defect in which a part of toner provided on the surface of the transferring material has a reverse polarity. Also, an image defect called a void is caused in a part of the surface of the transferring material. Also, in a case where the transfer/conveyance belt partly has a low volume resistivity, electric charge easily flows to a local area, in which the resistivity is low, in the surface of the belt. Consequently, the transferring material cannot be held through the electrostatic adsorption force.
Although a transferring voltage ranging from 1 kV to 5 kV is applied so as to cause the semiconductive belt to hold the transferring material and as to transfer the toner image onto the transfer material, the resistance value of the material of the belt changes due to the voltage applied thereto, so that the resistance value sometimes varies between a part, on which the transfer material is provided, and another part, on which no transfer material is provided, in the belt (that is, a belt resistance value variation sometimes occurs therein).
Meanwhile, rotating rolls, such as a charging roll, a transfer roll, a backup roll, a cleaning roll, and a development sleep, require the uniformity of the electrical resistance value, the nip pressure between the roll and each of an image carrier and an intermediate transfer member, and the width of the roll. Usually, a predetermined electrically conductive filling material is mixed into the material of the roll.